In an acknowledged mode (AM, Acknowledged Mode) of a Universal Mobile Telecommunications System (UMTS, Universal Mobile Telecommunications System), to transmit data between two radio link control (RLC, Radio Link Control) entities, a sender first sends RLC protocol data unit (PDU, Protocol Data Unit) data, which includes a poll (POLL) request; then a receiver feeds back a PDU reception status (Status PDU) according to the poll request, so as to inform the sender of PDUs that have been received and PDUs that have been lost; the sender performs selective retransmission according to the PDU reception status fed back by the receiver. To reduce the number of retransmission times and decrease a delay, the sender may actively send the Status PDU to request the receiver to move a receive window thereof, and delete a data packet to be retransmitted on the sender.
This technology can solve only a problem of a wait for retransmission at an RLC layer. In the Transmission Control Protocol (TCP, Transmission Control Protocol), a packet discarded actively at the RLC layer may lead to retransmission at a TCP layer, thereby resulting in a more severe delay. On the other hand, in the Real-Time Transport Protocol (RTP, Real-time Transport Protocol), an out-of-order RTP packet is also rearranged at an RTP layer; if a data packet is lost, a timer is also started, and the data packet is submitted to an upper layer again when waiting for the data packet already discarded actively at the RLC layer times out, thereby causing an unnecessary delay.
Another active packet discarding method is a TCP proxy method. A TCP proxy is established on an evolved NodeB (eNB, evolved NodeB) side to buffer a TCP stream transmitted by a server (Server); a new TCP connection is established between a user equipment (UE, User Equipment) and the eNB, and data to be transmitted is selected from a cache for sending, thereby achieving the purpose of active packet discarding.
However, in such a technical solution with the TCP proxy, a base station requires extra processing time and extra storage space to establish a new TCP connection. For a video application with a high requirement on real-time transmission reestablishment of a TCP connection causes an unnecessary delay and occupies an air interface resource.